Executioner's Guillotine Unique Finisher Effect Doesn't work with ailments

For the new finisher effect we got after watching a live stream for 2 hours, it only works when the last thing that kills a unique enemy is a hit from a weapon. If an ailment kills a unique enemy, even if it came from the basic attack of said weapon, it doesn't show.

Was this intended?

This was tested using Crossbow Shot Basic Bolt.

Actually, it started to work consistently with The Rust King, but for whatever reason just seems to work inconsistently with the unique enemies before that.

Not sure what the issue was.

I also got this effect from twitch drops. I cannot activate it in PoE 1. Is this effect actually only for PoE 2?